A mechanical shutter may be used in a digital, low cost, consumer electronic camera to control how long a complementary metal oxide semiconductor (CMOS) imaging sensor array of the camera is allowed to respond to light from a scene to capture a still image. When the shutter is open, light is allowed to accumulate on the sensor. The sensor is “exposed” during the time from deassertion of a reset signal (which electronically resets the sensors of the array), to the mechanical closing of the shutter (which physically covers the array). The length of time that the shutter remains open (from the deassertion of the reset signal) determines the length of time or exposure time during which photodetected charge can accumulate in the sensor. The shutter is closed after the time necessary for an exposure has elapsed. When the shutter is closed, it blocks the light from reaching the sensor. After the shutter closes, circuitry inside the camera moves an image (data) captured by the sensor to a storage area.
In contrast, modern, consumer electronic video cameras do not use a mechanical shutter but instead rely solely on the reset signal and a readout signal to end the exposure by electronically stopping or reading out the accumulation of photo-charge, to achieve a rapid sequence of exposures or frames. Typically, an electronic rolling shutter mechanism is used which “exposes” the CMOS sensor one row at a time (rather than all at once). This however can induce smearing artifacts into the capture of video (due to the fast movement in the scene).